Australian police on Monday said they had launched an international search for a man accused of pouring hot coffee on a nine-month-old baby, causing serious burns.

Queensland Police's Paul Dalton said a 33-year-old suspect fled the country days after committing "the most cowardly" crime the detective had seen in a decades-long career.

The baby was at a family picnic in a Brisbane park in late August when the man, believed to be an itinerant worker, poured scalding coffee over its face and limbs.

The baby "sustained serious burns" and required multiple surgeries.

Police have no idea what the man's motive was. He was not known to the family and is now believed to be in an unnamed country.

He is being accused of intending to cause grave bodily harm -- a charge that could carry a penalty of life in prison.

Dalton said "dogged and determined" police will not rest until the man is captured and faces justice.

"We will keep going until we find you," he said.

"(We are) fully committed to doing everything we possibly can lawfully to get this person back here to face justice."